Hi Davcom,

A noise level meter will measure the overall noise level, you can apply different weightings such A, B C or lin which is no weighting. You can get meters with built in frequcency analysers such as 1/3 octave analysis, which will give you an insight into the frequency spectra although narrow band analysis is better. I guess you are looking at interior cabin noise. To identify noise sources there are several techniques such as windowing and TPA (Transfer Path analysis). This requires more advance instrumentation and experience. Suppliers such as Bruel & Kjaer, LMS, Nosrsonic, etc sell this equipment. To get accruate, repeatable results a semi anechoic chamber is best to test the machine in. If it is engine noise that you are concerned with then some simple order tracking measurements will help identify any particular engine speeds where the noise is a problem. If you would like to discuss in more detail email me austinruby at msn dot com. I'm based in Ireland and worked as an NVH engineer before moving into the forklift business.